Chinese Premier Li Keqiang on Tuesday praised the former Japanese government official who issued a landmark apology over the wartime sexual slavery of Asian women, hailing his "bravery" in facing history.

Li greeted a trade delegation led by Yohei Kono, who as the country's top government spokesman in 1993 issued an eponymous statement acknowledging the military's involvement in a coercive "comfort women" brothel system during World War II.

He did not admit government complicity in it.

Relations between Beijing and Tokyo plunged in recent years over territorial disputes and wartime history. They are trying to rebuild ties but China's Communist leaders remain wary of Japanese Prime Minister Shinzo Abe's nationalist views.

"Mr Yohei Kono and this delegation have made great efforts towards improving Sino-Japanese relations, which especially makes me think of the Kono Statement that Mr Kono made that year, which showed a politician's bravery in shouldering the question of history," Li said in greeting the visitors.

Kono's visit comes ahead of the 70th anniversary of the end of World War II, and with China closely scrutinising the comments of the neighbour which invaded and occupied it in the 1930s and 1940s.

"It goes without saying that over the past two years Sino-Japanese ties have faced difficulties and both sides have the wish to improve things," Li said.

The Kono Statement was followed by an official 1995 apology by then-Prime Minister Tomiichi Murayama which said Japan "through its colonial rule and aggression, caused tremendous damage and suffering to the people of many countries, particularly to those of Asian nations". It added that the premier felt "deep remorse" and offered a "heartfelt apology".

The two documents together were "a basic principle for the Japanese government to correctly recognise history," Li said.

Kono responded that the visitors were "really very thankful" for the meeting with the Chinese premier.

Abe is expected to issue a new statement this year, with regional attention -- particularly in former Japanese colony South Korea, as well as China -- focused on any sign of backpedalling on earlier proclamations.

Despite a dearth of official records, mainstream historians say up to 200,000 women, many from the Korean peninsula but also from China, Indonesia, the Philippines and Taiwan, served as sexual slaves for Japanese soldiers in military brothels.

Most agree that the women were not willing participants and that the Imperial Japanese Army and wartime government were involved in their enslavement, tacitly or explicitly.

Japanese nationalists, however, say the women were common prostitutes engaged in a commercial exchange, and are fighting a vigorous rearguard battle to alter the narrative.

Also visiting China with Kono was Takeshi Onaga, governor of Japan's southern prefecture of Okinawa. Many Okinawans say it bears a disproportionate burden in hosting more than half of the 47,000 US service personnel stationed in Japan.

Onaga is at odds with Abe's government over the construction of a US air base, a long-running row that has defied easy solution despite agreements between Washington and Tokyo.